docs: def get_base_equivalent(self, unit_system=None):
          """Create and return dimensionally-equivalent units in a specified base.
  
          >>> from unyt import g, cm
          >>> (g/cm**3).get_base_equivalent('mks')
          kg/m**3
          >>> (g/cm**3).get_base_equivalent('solar')
          Mearth/AU**3
          """
          from unyt.unit_registry import _sanitize_unit_system
  
          unit_system = _sanitize_unit_system(unit_system, self)
          try:
              conv_data = _check_em_conversion(
                  self.units, registry=self.registry, unit_system=unit_system
              )
          except MKSCGSConversionError:
              raise UnitsNotReducible(self.units, unit_system)
          if any(conv_data):
              new_units, _ = _em_conversion(self, conv_data, unit_system=unit_system)
          else:
              try:
                  new_units = unit_system[self.dimensions]
              except MissingMKSCurrent:
                  raise UnitsNotReducible(self.units, unit_system)
          return Unit(new_units, registry=self.registry)